Installing the Ultra Series II Ultrasonic Antifouling system to your multi-hull boat will help to maintain the hull speed through the water and manoeuvrability, by reducing drag. Keeping the hull clear of growth reduces passage times, saving fuel and money. It can take up to 30% more fuel to push a fouled hull through the water – a significant factor for power catamarans!

The hull waterline length (LWL) is the main determining factor for the number of transducers that should be installed to the inside of the hull. Longer hulls will have a much larger underwater surface area to be considered for protection against fouling, so additional transducers will be required according to its length.

While sound waves are resonating throughout the hull form because the transducers are fixed to the inside of the hull, the stern gear (propellers, shafts and drives) are acoustically isolated from the sound within the hull due to the seals used in their attachment. In the proximity of a transducer, the ultrasound signal also dissipates out into the water in an 180o arc below the hull surface. Therefore, with correct positioning of transducers, the system can also help to some degree in keeping the stern gear clear, although not quite so effectively as the hull.

No through hull drilling is required, so the system can be installed with the boat in the water.

View the full Ultrasonic Antifouling product range

Recommended System Configurations

Catamaran: Same for both power and sail Catamarans.

Up to 10m LWL

Ultra 20 (one transducer in each hull) – price and options.

10m to 18m LWL

2 x Ultra 20 (two transducers in each hull) – price and options

18m to 24m LWL

3 x Ultra 20 (three transducers in each hull) – price and options


For a Trimaran multi-hull it can be considered that the centre hull requires Ultrasonic protection as it the hardest to maintain against fouling, while the two outer hulls have very little surface area in contact with the water which can usually be easily accessed and cleaned with a light brush.

For a suitable system configuration for the centre hull, it is recommended to install the same number of transducers as per each hull of a catamaran as shown above. i.e Up to 10m LWL: one transducer (Ultra 10).